A thermal sealing device is already known from the unexamined Japanese Patent Application H7-315310, where a film is warmed with a heater plate, a container (a cavity part) is molded by pressing the warmed film into a mold with compressed air, a package item is load in the container, the container's opening is covered with a capping film in a downstream stage, and the capping film's periphery is thermally sealed onto the container to complete the packaging process. However, it is impossible to measure the weight of the package item, whose weight is not uniform, during the packaging process. Therefore, it is usual to measure the weight of the product, including the container, after packaging it, to take the weight of the container away from the weight to calculate the weight of the package item, to print the calculated weight onto a label, and to stick the label on the container.
However, sticking the label after completing the packaging as described above in a prescribed position can be difficult, since it is possible that a portion of the top surface (capping film) of the heat-sealed container protrudes upwardly as the size and shape of the package item vary. Moreover, when a guide member is used to control the position of the container when the container is transferred by a conveyor, in order to control the label sticking position on the top surface of the container in case of sticking the label after completion of the packaging process as described above, the capping film and the container itself wrapped by the capping film may be soft, so that the container may not be able to be controlled to be transferred to the desired position even if the container comes in contact with the guide member, consequently causing a problem that it is difficult to stick the label printed with a weight on a uniform position of the package item after completion of the packaging process.